We have official data from General Motors for the 2027 Chevy Silverado 1500 and GMC Sierra 1500 MPG ratings. This includes the all-new 6th-generation 5.7L and 6.6L V8 engines. The MPG data is worse than we expected, and we have an explanation from GM. Let’s dig in.
Take a look at the table below for the 2027 GM 1500 mpg ratings. This also includes the 3.0L Duramax I6 turbo-diesel engine. The new and enhanced 2.7L Turbomax I4 engine ratings are not available yet, because this engine will be a delayed introduction. The 2.7L is a base engine and it will join the lineup in early 2027, according to GM.
Neither one of the new V8 engines reaches above 18 MPG highway rating when combined with a 4WD system. The 3.0L Duramax I6 shows impressive numbers, but the 2027 Duramax ratings are about 1 MPG lower than those for the 2026 models.
The 2026 Chevy Silverado 1500 with a 5.3L V8 and 2WD was rated at 16 city / 21 hwy /18 combined MPG. The new 5.7L 2WD truck offers 47 hp more than the 5.3L, but the MPG rating is 15 city / 19 hwy / 17 combined. The highway rating is 2 MPG worse than before.
The 2026 Silverado 1500 ZR2 4×4 with a 6.2L V8 was rated at 14 city / 17 hwy / 15 combined MPG. The new 2027 6.6L V8-powered ZR2 4×4 is rated at 13 city / 15 hwy / 14 combined MPG. Of course, the new 2027 Silverado 1500 ZR2 is rolling on bigger 35-inch all-terrain tires, and it’s making 61 hp more than before.
For comparison, the Ram RHO and the Ford F-150 Raptor trucks have better MPG ratings.
| Horsepower | City MPG | Hwy MPG | Combined MPG | |
| 2027 Silverado ZR2 | 481 hp V8 | 13 | 15 | 14 |
| 2027 Ram RHO | 540 hp TT I6 | 14 | 16 | 15 |
| 2026 F-150 Raptor | 450 hp TT V6 | 14 | 18 | 16 |
GM sent us the following statement as explanation.
“The fuel economy change from MY26 to MY27 is modest and configuration-specific. The new lineup represents a more capable, more highly equipped truck with a broader mix of customer choices. The new mileage estimates are based on trucks tested with the features and equipment our customers are increasingly choosing, including, for example, larger tire packages and lifted suspensions, versus previously tested models that may have had standard ride height and tires. The new figures better represent the trucks that customers are interested in buying, as opposed to the less-equipped versions that may have been tested before.
The 3.0L Duramax Turbo-Diesel is still the most fuel-efficient engine in its segment. 27 mpg highway / 24 mpg combined, and more than 900 miles of available highway range.
The 2027 Silverado 1500 lineup delivers more power, capability, refinement, safety and technology than before.
The new Silverado lineup has a broader mission and includes more content. This includes more lifted and off-road models (in line with customer preferences), higher output and capability, and substantially more standard equipment. The new engines use technologies such as higher compression, dual fuel delivery, Dynamic Fuel Management, and advanced thermal management to improve efficiency, emissions and real-world drivability.
The enhanced TurboMax also delivers more power and torque while remaining more fuel efficient than the larger V8s, and the Duramax remains the highest-fuel-economy engine in the industry, with more than 900 miles of available highway range.
The result of all the above is more meaningful choice. Customers can select the powertrain and configuration that best fits how they work, tow, commute or explore. For many truck buyers, capability, value, durability, confidence and versatility are central to the purchase decision. We designed the 2027 Silverado to deliver more of those attributes while continuing to offer an efficient TurboMax and the segment’s only diesel powertrain.“
